Self-propelled scaffold



Oct. 4, 1966 P. POMMIER SELF-PROPELLED SCAFFOLD 2 Sheets-Sheet 1 Filed June 22, 1965 INVENTOR PIERRE POMM/ER BY Mia and BMW/1 AGENTS Oct. 4, 1966 P. POMMIER 3,276,542

SELF-PROPELLED SGAFFOLD Filed June 22, 1965 2 Sheets-Sheet 2 FIG.

INVENTOR I P/ERR E POM/HER me/MW AGENTS United States Patent Office 3 ,276,542 Patented Oct. 4, 1966 16,16 Claims. (Cl. 182-16) This invention relates to scaffolds for supporting a workman in an elevated position, and particularly to a scaffold which can be moved on the ground or another supporting surface by the workman while he is supported on the platform, such a scaffold being referred to herein as a self-propelled scaffold.

The scaffolds with which this invention is more particularly concerned are useful in the field of building construction where they may support workmen painting a ceiling or doing other work above the floor which requires displacement of the workers in a horizontal direction. Ladders and similar devices cannot safely be moved while supporting a person, and ordinary wheeled platforms require the services of a helper if the work is not to be interrupted for a relatively long period for each displacement of the platform. The utility of the scaffolds of the invention is not limited to construction work, and they are used to good advantage in aircraft maintenance work.

The basic object of the invention is the provision of a platform that may be held at any desired height within a practical range, which is stable and permits a workman standing on the platform to move freely without danger of toppling the platform and its supporting framework, and which may be moved by the workman along the ground or other supporting surface without descending from the platform.

In its basic aspects, the scaffold of the invention therefore includes a platform which is supported in a normally horizontal position on a normally upright framework. Two rear wheels are rotatably mounted on the framework which also carries a steering column angularly movable about a normally upright axis and capable of axial translatory movement on the framework. Two front wheels are mounted on the column, and the several wheels are arranged for rotation in normally upright planes. Handles accessible from the platform permit the steering column to be moved angularly about its axis, and an automatic brake is respectively associated with each front wheel selectively to arrest rotation of the associated front wheel in one direction. The framework also carries two front legs and is equipped with a shifting device which permits the front legs and front wheels to be shifted between two positions. In the first position, the four wheels are adapted to engage a supporting surface while the front legs are upwardly spaced from that surface, while in the second position the rear wheels and front legs are adapted to engage that surface. The shifting device includes a linkage which operatively connects the front legs and front wheels, is movably mounted on the framework, and is accessible from the platform.

Other features and many of the attendant advantages of this invention will become apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered with the attached drawing in which:

FIG. 1 shows a self-propelled scaffold of the invention in a perspective view, most elements of the scaffold being in their normal operative position;

FIG. 2 shows a shifting linkage of the scaffold of FIG. 1 and associated elements in a side-elevational sectional view on a larger scale;

FIG. 3 shows a front wheel of the scaffold and a portion of the front axle in side elevation and partly in section on the scale of FIG. 2; and

FIG. 4 shows the scaffold in the collapsed condition ready for transportation or storage, the view corresponding to that of FIG. 1.

The scaffold of the invention, as seen in FIG. 1, has a normally upright front frame 1 of elongated rectangular shape. Each longitudinal upright frame member has a cylindrical tubular top portion 2 in which a lower portion 3 is slidably received. The two portions are adjustably secured to each other by a locking pin 4 which passes through two diametrically opposite openings in the top portion 2 and through one of several corresponding, longitudinally spaced openings (not shown) in the lower portions 3. Two fixed legs 5 extend downward from the lower transverse frame member 6 which connects the two lower portions 3.

Two longitudinal members of a rear frame 7 are attached to the upper transverse member 8 of the front frame by two pivots 10. Each longitudinal member of the rear frame consists of an upper portion 11 and a lower portion 12 which are also secured in telescoping engagement by a locking pin 4. The lower portions 12 are connected by a tubular transverse member 13 in which two axles 14 are slidably mounted. Each axle carries a rear wheel 15, and may be fixed in the member 13 by a clamping screw 18.

Two transverse frame members 16, 17 fixedly connect the top portions 2 of the front frame 1 and the upper portions 11 of the rear frame 7 respectively on a common horizontal level below the pivots 10. The front edge of a platform 19 is attached to the transverse member 16 by strong hinges 20 (FIG. 2). Hooks 21 on the rear edge of the platform engage the transverse member 17 in the operative position of the scaffold so as to secure the two frames 1, 7 to each other in fixed angular relationship. The longitudinal members of the rear frame 7 are normally conformingly received in notches 22 in the rear edge of the platform 19.

Two short links 23 are hingedly secured near the center of the transverse frame member 16. They are respectively connected to the free ends of a U-shaped pedal 24 'by pivot pins 25, as is best seen in FIG. 2. A pin 26, which connects the arms of the pedal 24, pivotally carries a bearing sleeve 28. Similar sleeves 29, 30 are fixedly attached to the upper transverse member 8 and to the lower transverse member 6 of the front frame.

The upper tubular portion 31 of a steering column is journaled in the sleeves 28, 29, and the lower steering column portion 32 is journaled in the sleeve 30 and is telescopically received in the upper portion 31 with which it is adjustably connected by a locking pin 4. The steering oolumn is rotatable and axially slidable in the bearing sleeves. The sleeve 28 normally rests on a fixed collar 33 on the steering column portion 31.

The top of the steering column carries a cross bar 34 whose ends are equipped with handle grips 35. A heavy casing 36 is fixedly attached to the bottom of the steering column and is slotted in a plane which includes the axis of the steering column. The slot 37 in the casing 36 is downwardly and laterally open. An axle 38 passes through the slot 37 and is pivotally attached to the casing 36 in the slot 37 by a pin 40. The width of the slot 37 is only insignificantly greater than that of the axle 38, wherein the axle is capable of limited pivoting movement in a vertical plane on the pin 40, but cannot move horizontally relative to the steering column.

The ends of the axle 38 respectively carry two front wheels 41 on stationary shafts 39, as shown in detail in FIG. 3. Each wheel has a rubber tread 42 and is equipped with a simple automatic brake which permits rolling movement of the wheel in one direction while preventing rota 3 tion in the opposite direction. The brake consists of a hook member 43 which is pivotally attached to the axle 38 by a pin 44 and whose free hooked end 45 envelops the tread 42. The axes of the shaft 39 and of the pin 44 are parallel, and spaced from each other, whereby the free end 45 engages the tread 42 and selectively arrests rotation of the wheel 41 in the direction of the arrow 46.

The scaffold is normally stored and transported in the collapsed condition shown in FIG. 4 in which the hooks 21 are disengaged from the transverse rear frame member 7, and the platform 19 is pivoted toward the lower portion of the front frame 1. The front frame 1, rear frame 7, and steering column 31, 32 are reduced to their minimum height by telescoping movement of their longitudinal members, and the front and rear frames are moved close to each other about the pivots 10.

The scaffold is made ready for use in a few minutes by first pivoting the front and rear frames apart until the platform 19 can be hooked over the transverse rear frame member 17, thereby to secure the two frames in a fixed angular relationship. The steering column and the several longitudinal frame members are next extended to the desired length, and secured in their extended positions by the locking pins 4. The axles 14 and the rear wheels 15 are pulled out of the tubular member 13 as indicated in broken lines in FIG. 1 in order to broaden the base of the scaffold and to improve its stability under adverse conditions of loading. The scaffold is then turned upright.

The vertical spacing of the platform 19 from the pivots 10 is the same regardless of the overall length of the upright scaffold members. The parts of the rear frame members 11 nearest the pivots 10 are approximately horizontal in the normal operating position of the scaffold and form lateral guard rails for a workman standing on the platform 19.

While Work is being performed, the front end of the scaffold rests on the legs 5. The front Wheels 41 may touch the floor but they merely support the Weight of the steering column 31, 32. The bearing sleeve 28 and the collar 33 may be vertically spaced from each other in the working position of the scaffold, but this is not necessary nor actually desirable.

When the workman wishes to move the scaffold, he does not have to descend from the platform 19. He places a foot on the pedal 24 and pivots the same counterclockwise, as viewed in FIG. 2, on the pins 25, 26. The bearing sleeve 28 is thereby displaced downward relative to the platform 19 and the frame members 2. The legs 5 are lifted off the ground, and the weight of the scaffold front is transferred to the front wheels 41. The vertical relative movement of the legs 5 and the wheels 41 necessary for the aforedescribed transfer of weight need not be greater than about one inch, and may be chosen between one and two inches in order to allow adequately for unevenness and minor obstacles on the ground over which the scaffold travels. The difference in length between the two lever arms of the pedal 24 on either side of the pin 26 may thus be chosen much greater than in the illustrated embodiment of the invention if the weight of the scaffold and of the load supported thereon should so require for easy operation of the pedal.

. While holding the wheels 41 in load-bearing engagement with the ground by means of the pedal 24, the workman standing on the platform 19 then oscillates the cross bar 34 in a horizontal plane through an angle which should be smaller than 90 if movement in an approximately straight forward path is desired. Actually, the scaffold moves in arcuate steps, the left front wheel rolling forward and the right front wheel being arrested by its brake hook 43 while the handle grips 35 are moved clockwise, as viewed from above, and only the left wheel rolling and vice versa during counterclockwise movement of the handle grips 35. If the scaffold is to turn, the strokes of the cross bar 34 in one direction are made longer than those in the other direction The scaffold may also be moved backward by oscillating the cross bar 34 after the steering column has been turned The pivoting attachment of the front axle 38 to the steering column portion 32 by the pin 40 is essential to make the propelling and steering mechanism fully effective where the scaffold has to travel over small obstacles of the type unavoidable on a building site, or on the run ways of an airport, or over a building floor which is not perfectly flat. If one of the four wheels 15, 41 moves over a pebble, a piece of lath, or a raised portion of the floor of a height sufficient not to be compensated for by the rubber treads 42, the load would be removed from one of the front wheels 41 in the absence of the pivot at the pin 40. The unloaded wheel would not provide a stationary support about which the axle 38 may swing while the other wheel rolls. The scaffold would be swung backward about the last-mentioned wheel. A scaffold of the general type illustrated but lacking the pivotal attachment of the front axle therefore cannot be propelled effectively over ground whichis not reasonably flat.

This difficulty cannot be avoided by using a single rear wheel, because the stability of a three-wheeled scaffold is insufficient for many purposes such as those which re quire a broad base as provided by the extensible rear axles 14.

It should be understood, of course, that the foregoing disclosure relates only to a preferred embodiment of the invention, and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purpose of the disclosure whichdo not constitute departures from the spirit and scope of the invention set forth in the appended claims.

What is claimed is: v

1. A self-propelled scaffold comprising, incornbina-v tion:

(a) frame means adapted to stand in a normally upright position;

('b) a normally horizontal platform supported on said frame means;

(0) two rear wheels rotatable on said frame means in normally upright planes spaced from each other;

(d) two front legs on said frame means; F

(e) a steering column mounted on said frame means for angular movement about a normally upright axis;

(f) handle means accessible from said platform for manually actuating said angular movement; (g) two wheels mounted on said steering column for rotation in respective, spaced, normally upright planes;

(h) automatic brake means associated with each of said front wheels for selectively arresting rotation of the associated front wheel in a predetermined direction; and

(i) shifting means for shifting said front wheels relative to said front legs between a first normal position in which said front and rear wheels are adapted to engage a supporting surface while said front legs are upwardly spaced from said surface, and a second norrnal position in which said front legs and rear wheels are adapted to engage said surface, 7 4

(1) said shifting means including a shifting link age movably mounted on-said frame and acces sible from said platform, said linkage operatively connecting said front legs and said front wheels for movement relative to each other.

2. A scaffold as set forth in claim 1, .wherein said frame means and said column include respective upper and lower portions movable relative to each other in a normally up:

right direction and locking means for securing said portions in a plurality of relative'positions spaced from each other in said upright direction, said platform being se'-' cured to theupper portion of said frame means.

B. A scaffold as set forth in claim 1, wherein said frame means include a front frame and a rear frame, said frames being elongated in an upward direction in the normal position thereof and having respective upper and lower portions; pivot means connecting said upper portions of said frames for movement about a normally horizontal axis, said platform being hingedly attached to the upper portion of one of said frames and being downwardly spaced from said pivot means; releasable means on said platform for securing the same to the upper portion of the other frame, said upper and lower portions of each frame being longitudinally movable relative to each other in telescoping engagement; and locking means for selectively securing said frame portions to each other in a plurality of relative longitudinal positions.

4. A scaffold as set forth in claim 3, wherein said linkage includes a lever member pivotally attached to the upper portion of said one frame and having a portion upwardly adjacent said platform.

5. A scaffold as set forth in claim 1, further comprising a front axle, having a central portion and two terminal portions spaced from said central portion in opposite directions and respectively carrying said front wheels, and pivot means securing said central portion to said steering column for limited pivoting movement in a normally upright plane.

6. A scaffold as set forth in claim 1, further compris ing two elongated rear axles mounted on said frame means for longitudinal movement in a direction transverse of the planes of rotation of said rear wheels, said rear wheels being respectively mounted on said rear axles.

7. A scaffold as set forth in claim 1, further comprising front axle means mounted on said steering column, each front wheel being secured to said axle means for rotation about an axis, and having a peripheral tread, and the brake means associated with said front wheel including a hook member secured to said axle means for pivoting movement about an axis spaced from the axis of rotation of the front Wheel and having an end portion hooked about the tread of the associated front wheel for movement toward and away from said tread during said pivoting movement of said hook member.

'8. A self-propelled scaffold comprising, in combination:

(a) a front frame and a rear frame, each frame having an upper portion and a lower portion, said frames being elongated and the two portions thereof being in telescopic engagement for relative longitudinal movement;

(b) locking means for securing the two portions of each frame to each other in a selected longitudinal relationship;

() a pivot connecting the upper portions of said frames for movement of the lower portions thereof toward and away from each other;

(d) securing means for securing said frames in fixed angular relationship relative to said pivot,

(1) said securing means including a platform member hingedly attached to the upper portion of said front frame, and

(2) releasable means for securing said platform member to the upper portion of said rear frame;

(e) a steering column elongated in the direction of elongation of said front frame, said steering column being mounted on said frame for rotary movement about a'longitudinal axis and for axial translatory movement, and having an upper longitudinal portion and a lowerv portion;

(f) handle means on said column above said platform member for actuating said rotary movement of said column;

(g) -a front axle having a central portion and two terminal portions spaced from said central portion in two opposite directions transverse of the direction of elongation of said column;

(h) pin means connecting said central portion of said front axle to the lower portion of said steering column for pivotal movement of said front axle on said column;

(i) two transversally spaced rear wheels on said lower portion of said rear frame;

(j) a front wheel on each terminal portion of said front axis;

(k) two transversely spaced front legs on the lower portion of said front frame and (l) shifting means for shifting said front frame toward and away from a position relative to said steering column in which said front wheels downwardly project beyond said front legs;

(1) said switching means including a lever memher,

(2) first pivot means on said steering column,

( 3) collar means for limiting downward movement of said first pivot means on said steering column,

(4) second pivot means on said said front frame,

(5) respective spaced first and second portions of said lever member being fastened to said first and second pivot means for pivotal movement of said lever member relative to said steering column and to said front frame, and

(6) a third portion of said lever member extending from one of said pivot means in a direction away from the other pivot means, the length of said third portion being substantially greater than the spacing of said first and second pivot means, said third portion being closely adjacent said platform member.

9. A scaffold as set forth in claim 8, wherein said portions of said steering column are longitudinally movable relative to each other in telescoping engagement.

10. A scaffold as set forth in claim 8, wherein said third portion of said lever member is located above said platform member when said platform member is secured to said rear frame by said releasable means.

upper portion of References Cited by the Examiner UNITED STATES PATENTS 2,237,688 4/1941 LPhillips 18216 2,923,373 2/1960 Ledgerwood 182l7 2,989,139 6/1'961 Pantek 182-46 REINALDO P. MAOHADO, Primary Examiner. 

1. A SELF-PROPELLED SCAFFOLD COMPRISING, IN COMBINATION: (A) FRAME MEANS ADAPTED TO STAND IN A NORMALLY UPRIGHT POSITION; (B) A NORMALLY HORIZONTAL PLATFORM SUPPORTED ON SAID FRAME MEANS; (C) TWO REAR WHEELS ROTATABLE ON SAID FRAME MEANS IN NORMALLY UPRIGHT PLANES SPACED FROM EACH OTHER; (D) TWO FRONT LEGS ON SAID FRAME MEANS; (E) A STEERING COLUMN MOUNTED ON SAID FRAME MEANS FOR ANGULAR MOVEMENT ABOUT A NORMALLY UPRIGHT AXIS; (F) HANDLE MEANS ACCESSIBLE FROM SAID PLATFORM FOR MANUALLY ACTUATING SAID ANGULAR MOVEMENT; (G) TWO WHEELS MOUNTED ON SAID STEERING COLUMN FOR ROTATION IN RESPECTIVE, SPACED, NORMALLY UPRIGHT PLANES; (H) AUTOMATIC BRAKE MEANS ASSOCIATED WITH EACH OF SAID FRONT WHEELS FOR SELECTIVELY ARRESTING ROTATION OF THE ASSOCIATED FRONT WHEEL IN A PREDETERMINED DIRECTION; AND (I) SHIFTING MEANS FOR SHIFTING SAID FRONT WHEELS RELATIVE TO SAID FRONT LEGS BETWEEN A FIRST NORMAL POSITION IN WHICH SAID FRONT AND REAR WHEELS ARE ADAPTED TO ENGAGE A SUPPORTING SURFACE WHILE SAID FRONT LEGS ARE UPWARDLY SPACED FROM SAID SURFACE, AND A SECOND NORMAL POSITION IN WHICH SAID FRONT LEGS AND REAR WHEELS ARE ADAPTED TO ENGAGE SAID SURFACE, (1) SAID SHIFTING MEANS INCLUDING A SHIFTING LINKAGE MOVABLY MOUNTED ON SAID FRAME AND ACCESSIBLE FROM SAID PLATFORM, SAID LINKAGE OPERATIVELY CONNECTING SAID FRONT LEGS AND SAID FRONT WHEELS FOR MOVEMENT RELATIVE TO EACH OTHER. 